KR20100088159A - Method of manufacturing permanent magnet - Google Patents

Abstract

Provided is a method for producing a permanent magnet having an extremely high orientation by allowing the crystal wavefronts of raw material powders having more identical crystal orientation relations in the magnetic field to be combined. In the present invention, the raw material powder P is filled in the cavity 22, and the raw material powder P is oriented in a magnetic field while pressing the raw material powder P with the pressing means 5 having an area smaller than the cross sectional area of the cavity. The oriented one is compression molded into a predetermined shape in a magnetic field.

Description

Method of manufacturing permanent magnets {METHOD OF MANUFACTURING PERMANENT MAGNET}

The present invention relates to a method for producing a permanent magnet, and more particularly, to a method used in the production of Nd-Fe-B-based permanent magnet having a high orientation.

Nd-Fe-B-based sintered magnets (so-called neodymium magnets) are made of a combination of iron and elements of Nd and B, which are inexpensive, resource-rich and stable, and can be manufactured at low cost. Because of its high magnetic properties (maximum energy is about 10 times that of ferrite magnets), it is used in various products such as electronic devices, and is also used in motors and generators for hybrid cars, and its usage is increasing.

Nd-Fe-B-based magnets are mainly produced by powder metallurgy. In this method, first, Nd, Fe and B are blended in a predetermined composition ratio, melted and cast to produce an alloy raw material. Roughly grind | pulverizes by a hydrogen grinding process, and then, finely grind | pulverizes, for example by a jet mill fine grinding process, and obtains a raw material powder. Next, the obtained raw material powder is orientated (magnetic field orientation) in a magnetic field, and it is compression-molded in the state which applied the magnetic field, and a molded object is obtained. Then, the molded body is sintered under predetermined conditions to produce a sintered magnet.

Generally as a compression molding method in a magnetic field, a uniaxial press type compression molding machine is used, and this compression molding machine fills a cavity (filling chamber) formed in the through-hole of a die, and uses a pair of upper and lower punches. It is pressurized from the up and down direction to form a raw material powder, but in compression molding using a pair of punches, friction between particles in the raw material powder filled in the cavity, wall surface of the mold set to the raw material powder and the punch and There was a problem in that high orientation could not be obtained due to friction, and the magnetic properties could not be improved.

From this, the compression molding method which fills a cavity with raw material powder, and vibrates at least one of an upper punch and a lower punch at the time of magnetic field orientation in a pressurizing direction (press direction) is known. In this compression molding method, a magnetic field is applied while vibrating the raw material powder with the upper punch or the lower punch, and the friction between the particles in the raw material powder is changed from the static friction to the dynamic friction in the raw powder filled in the cavity. Since the raw material powder can be reduced to reduce the fluidity of the raw material powder and be more aligned in the magnetic field alignment direction, the orientation can be improved (Patent Document 1).

Patent Document 1: International Publication No. 2002/60677 (for example, see description of claims)

However, in the compression molding method, since the vibration is caused by one of the upper punch and the lower punch at the time of magnetic field orientation, the positional relationship between the particles of the raw material powder in the cavity does not change most from the state filled in the cavity. For this reason, crystal wavefronts (Nd-Fe-B-based sintered magnet powders) of particles of raw material powders adjacent to each other in the magnetic field orientation direction are prepared by blending Nd, Fe, and B, dissolving, alloying, and then pulverizing them. Therefore, when the crystal wavefront having no specific cleavage surface is formed on the surface of the raw material powder), a gap is left between the particles of the raw material powder, so that the raw material powder is easily magnetized in the magnetic field orientation direction. There is a problem that the axis is not aligned, and the compression molding in this state causes the orientation to be disturbed.

In view of the foregoing, an object of the present invention is to provide a method for producing a high performance permanent magnet made of an oriented body, a molded body and a sintered body having extremely high orientation by combining powder crystal wavefronts having a more identical crystal orientation relationship in a magnetic field or an electric field. To provide.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the manufacturing method of the permanent magnet of Claim 1 fills a raw material powder to a filling chamber, and pressurizing means which has an area smaller than the cross-sectional area of the said filling chamber with respect to this raw material powder. It comprises an orientation step of aligning in the magnetic field while pressing and a molding step of compression molding the oriented thing into a predetermined shape in the magnetic field.

According to the invention of claim 1, after the raw material powder is filled into the filling chamber, the magnetic field is oriented in the magnetic field. At this time, the pressing means is pressed against the raw material powder in the filling chamber at a predetermined pressure from the same direction as the filling direction of the raw material powder in the filling chamber, for example. Here, since the area of the contact surface (pressing surface) with the raw material powder of this pressing means is set smaller than the cross sectional area of the filling chamber, when the pressing means is pressed against the raw powder, the space between the pressing means and the inside of the filling chamber is pressed. Raw material powder is pushed.

As a result, the bonding between the particles when the magnetic field is applied is broken once, and the positional relationship between the particles of the raw material powder in the filling chamber changes from the state filled in the filling chamber. And among the combination of crystal wavefronts in the magnetic field orientation direction, there are more opportunities for the crystal wavefronts having the same crystal orientation relationship to be combined, and once the crystal wavefronts having the same crystal orientation relationship combine, they form a strong binding chain. In the magnetic field orientation direction, crystal wavefronts are joined without gaps. Then, the crystal wavefront is bonded in the magnetic field orientation direction without gaps and compression molded to form a high-density permanent magnet without disorder of orientation, and a high-performance magnet can be obtained.

In the invention according to claim 1, the raw material powder is further mixed in the filling chamber by changing the positions of the pressing means in order so that the pressing means is pressed down over the entire cross section of the filling chamber. By changing the positional relationship between the particles in the inside, there may be more opportunities to combine the crystal wavefront having the same crystal orientation relationship. This is particularly effective when the cross section of the filling chamber is rectangular.

Moreover, when pressing down the said press means, you may make it vibrate in the pushing direction.

In this case, when the lubricating agent is added to the raw material powder at a predetermined mixing ratio and mixed, the filling is performed in the bag, whereby the fluidity of the raw material powder is improved.

Moreover, in order to prevent adhesion of the raw material powder to the pressing means, the pressing means is preferably a nonmagnetic material.

Moreover, in order to solve the said subject, the manufacturing method of the permanent magnet of Claim 6 WHEREIN: The process of filling a raw material powder in the bag with which deformation | transformation is free, and knead | mixing the raw material powder in a bag by applying a local pressure to the said bag. And the step of orienting in a magnetic field and the step of compression molding the oriented raw material powder into a predetermined shape in a magnetic field.

According to the invention of claim 6, after the raw material powder is filled into the bag, the magnetic field is oriented in the magnetic field. At this time, the raw material powder in the bag is kneaded by applying a pressing force locally at a plurality of places with respect to the bag free of deformation. As a result, the bonding between the particles when the magnetic field is applied is broken once, and the positional relationship between the particles of the raw material powder in the bag changes from the state filled in the filling chamber. And among the combination of crystal wavefronts in the magnetic field orientation direction, there are more opportunities for the crystal wavefronts having the same crystal orientation relationship to be combined, and once the crystal wavefronts having the same crystal orientation relationship combine, they form a strong binding chain. In the magnetic field orientation direction, the crystal wavefront is joined without gaps and arranged. Then, the crystal wavefront is bonded without gaps in the magnetic field alignment direction and compression molded to provide a high-density without disorder of orientation, thereby obtaining a high performance magnet.

In this case, when the lubricant is added to the raw material powder at a predetermined mixing ratio and mixed, the filling chamber is charged to improve the fluidity of the raw material powder.

In addition, in the said invention, it is preferable to include the sintering process which sinters the oriented or compression molded thing in addition to the said molding process or instead of the said molding process.

Moreover, if the said raw material powder is for the rare earth magnet produced by the quenching method, the raw material powder becomes angular particle shape, the area of a crystal wavefront can be enlarged, the clearance between the particle | grains of raw material powder can be made small, In addition to increasing the chance of combining the crystal wavefronts of the raw material powder having the same crystal orientation relationship, the orientation can be made extremely high.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the compression molding machine which implements the manufacturing method of 1st Embodiment of this invention in a standby position.
It is a figure explaining the state which moved the press means with respect to the compression molding machine shown in FIG.
3 is a view for explaining the position of the pressing means with respect to the cavity.
4 (a) to 4 (f) are diagrams illustrating the operation (orientation step) of the pressing means.
Fig. 5A is a diagram illustrating the magnetic field orientation of the prior art. FIG. 5B is a diagram illustrating the magnetic field orientation in the first embodiment. FIG.
It is a figure explaining the shaping | molding process of the compression molding machine shown in FIG.
It is a figure explaining the compression molding machine which implements the manufacturing method of 2nd Embodiment of this invention in a standby position.
It is a figure explaining the state which the kneading means moved with respect to the compression molding machine shown in FIG.
It is a figure explaining the kneading of the raw material powder in a bag by kneading means.
Fig. 10 (a) is a diagram illustrating the magnetic field orientation of the prior art. FIG.10 (b) is a figure explaining the kneading magnetic field orientation in 2nd Embodiment.
It is a figure explaining the shaping | molding process of the shaping | molding apparatus shown in FIG.
12 (a) is a table which shows conditions, such as a shape of a press means, the number of times of pressing, etc., (b) is a table which shows the magnetic characteristic and orientation of the sintered magnet produced by Example 1. FIG.
13 is a table showing the magnetic properties and the orientation of the sintered magnet produced in Example 2. FIG.

EMBODIMENT OF THE INVENTION Hereinafter, with reference to drawings, the compression molding machine 1 suitable for manufacturing the rare earth permanent magnet of 1st Embodiment of this invention, especially the sintered magnet of Nd-Fe-B system is demonstrated. The compression molding machine 1 is a uniaxial pressurized type in which the pressing direction Y (press direction) is perpendicular to the magnetic field alignment direction, and has a base plate 12 supported by the leg portion 11. The die 2 is disposed above the base plate 12. The die 2 is supported by a plurality of struts 13 penetrating the base plate 12, and the other end of each strut 13 is connected to a connecting plate 14 provided below the base plate 12. . The connecting plate 14 is connected to a drive means, for example a cylinder rod 15 of a hydraulic cylinder of a known structure. As a result, when the lower hydraulic cylinder is operated to raise and lower the connecting plate 14, the die 2 is movable in the vertical direction in FIG. 1, which is the pressing direction Y. FIG.

A through-hole 21 in an up-down direction is formed in the substantially center portion of the die 2, and a lower punch (25) is installed in the through-hole 21 upwardly from the bottom of the base plate 12 in an approximately center portion thereof. 31 can be inserted, and when the lower hydraulic cylinder is operated to lower the die 2, the lower punch 31 is inserted into the through hole 21 and the cavity (charge chamber) 22 into the through hole 21. Is provided. The cross-sectional shape of the through hole 21 (cavity 22) is appropriately selected depending on the shape of the sintered magnet to be molded, such as a circle or a rectangle. In this embodiment, in order to produce a rectangular parallelepiped sintered magnet, the cross-sectional shape is formed in rectangle. As for the cavity 22, the powder supply apparatus of a well-known structure (not shown) is free to move in and out, and the powder supply apparatus is filled with the alloy powder material described below, which is weighed in advance, (see Fig. 2). ).

The die base 16 is disposed above the die 2 so as to face the base plate 12. The upper punch 32 is provided in the lower surface of the die base 16 in the position which can be inserted in the cavity 22. Moreover, the through-hole of the up-down direction is formed in the edge part of the die base 16, and the guide rod 17 whose one end was fixed to the upper surface of the die 2 is inserted through each through-hole. In addition, a drive means, for example, a cylinder rod 18 of a hydraulic cylinder (not shown) of a known structure is connected to the upper surface of the die base 16, and when the hydraulic cylinder is operated, the guide rod 17 is guided. The die base 16 can move up and down, and furthermore, the upper punch 32 is free to move up and down, and can be inserted into the through hole 21 of the die 2. Thereby, at the time of compression molding, the raw material powder P is compressed by a pair of upper and lower punches 31 and 32 in the cavity 22 to obtain a molded body (molding step).

Moreover, the magnetic field generating device 4 is provided in the outer periphery of the die 2 in order to orient the raw material powder P in the cavity 22. The magnetic field generating device 4 is symmetrically arranged so as to sandwich the die 2 from both sides, and a pair of yokes 41a and 41b made of a material having a high permeability such as carbon steel, mild steel, pure iron or permendur. ) Coils 42a and 42b are wound on both yokes 41a and 41b and energized by coils 42a and 42b, whereby a static magnetic field is generated in the direction X orthogonal to the pressing direction (up-down direction Y). In this way, the raw material powder P filled in the cavity 22 can be oriented.

Here, the raw material powder P is produced as follows. That is, Fe, B, and Nd are mix | blended in a predetermined composition ratio, and the alloy of 0.05 mm-0.5 mm is produced first by a quenching method, for example, the strip cast method. On the other hand, an alloy having a thickness of about 5 mm can be produced by centrifugal casting, and a small amount of Cu, Zr, Dy, Al, or Ga can be added during compounding. Next, the produced alloy is coarsely pulverized by a well-known hydrogen grinding | pulverization process, and then it is pulverized in nitrogen gas atmosphere by a jet mill pulverization process, and raw material powder of an average particle diameter of 2-10 micrometers is obtained. In this case, when the quenching method is used, the raw material powder P becomes an angular particle shape, the area of one crystal wavefront can be enlarged, and the clearance gap between raw material powders P can be made small.

In order to improve the fluidity | liquidity of the said raw material powder P, the raw material powder P produced as mentioned above adds a lubricating agent to the raw material powder P at a predetermined | prescribed mixing ratio, and this raw material powder P The surface of is covered. As the lubricant, a low viscosity solid lubricant or a liquid lubricant is used so as not to damage the mold.

As a solid lubricant, layered compounds (MoS ₂ , WS ₂ , MoSe, graphite, BN, CFx, etc.), soft metals (Zn, Pb, etc.), hard materials (diamond powder, TiN powder, etc.), organic polymers (PTEE-based, nylon-based) Aliphatic, higher aliphatic, fatty acid amide, fatty acid ester, metal soap, etc.), and zinc stearate, ethylene amide, and fluoroether grease are particularly preferred.

Examples of the liquid lubricant include natural fats and oils (plant oils such as castor oil, palm oil, palm oil, mineral oil, petroleum-based fats and oils), and organic low molecular weight materials (lower aliphatic, lower fatty acid amide, lower fatty acid ester). It is preferable to use a liquid fatty acid, a liquid fatty acid ester, and a liquid fluorine-based lubricant. The liquid lubricant is used together with a surfactant or diluted with a solvent, and since the residual carbon component of the lubricant remaining after sintering lowers the coercive force of the magnet, a low molecular weight material is preferred for easy removal in the sintering process.

Moreover, when adding a solid lubricant to gold raw material powder P, what is necessary is just to add in 0.02 wt%-0.5 wt% mixing ratio. If it is less than 0.02 wt%, the fluidity of the raw material powder P does not improve, and consequently, the orientation does not improve. On the other hand, when it exceeds 0.1 wt%, when a sintered magnet is obtained, the coercive force decreases under the influence of the carbon remaining in the sintered magnet. Moreover, when adding a liquid lubricant to raw material powder P, what is necessary is just to add in the ratio of 0.05 to 5 wt%. If it is less than 0.05 wt%, there is a possibility that the flowability of the raw material powder does not improve, and eventually the orientation cannot be improved. On the other hand, if it exceeds 5 wt%, when the sintered magnet is obtained, the residual carbon in the sintered magnet Affected reduces coercive force. In addition, when both a solid lubricant and a liquid lubricant are added to a lubrication agent, a lubrication agent spreads to every corner of raw material powder P, and a higher orientation can be obtained by a higher lubrication effect.

In addition, after the compression molding machine 1 fills the cavity 22 which is a filling chamber with the raw material powder P containing a lubricant, it precedes compression molding (molding process) by a pair of upper and lower punches 31 and 32. In the state where the magnetic field is generated by energizing each of the coils 42a and 42b of the magnetic field generating device 4 (in the magnetic field), the magnetic field can be oriented while mixing the raw material powder P in the cavity 22 (orientation). Process), the pressing means 5 which is free to advance and retreat with respect to the cavity 22 is provided.

As shown in FIG. 2, the pressing means 5 has the fixed frame 51 and the lifting frame 53 which move up and down freely through the guide rod 52 through the fixing frame 51, and are movable in an up-down direction. It consists of. A cylinder 54 is mounted on the fixed frame 51, and a piston rod 54a extending downward from the cylinder 54 is connected to the lifting frame 53. The lifting frame 53 is moved up and down by the cylinder 54. A guide rail 55 extending in a direction orthogonal to the moving direction of the piston rod 54a is formed on the lower surface of the lifting frame 53, and a movable frame 56 is provided on the guide rail 55.

The pressing member 57 is connected to the movable frame 56 so that it may extend along the up-down direction Y. As shown in FIG. The pressing member 57 is a member of a solid square pyramid, and is made of a nonmagnetic material such as PEEK, engineering plastics such as nylon, and 18-8 stainless steel. Thereby, raw material powder P adheres and mixing of raw material powder P becomes inadequate, or a magnetic field can be prevented from being disturbed. The cross sectional area of the pressing member 57 is a cross sectional area of the cavity 22 such that a predetermined space is formed between the wall surface of the cavity 22 when the raw material powder P is pressed by the pressing member 57. It may be smaller, but considering workability, it is preferable to set it to about 1 / 2-1 / 16 (1/2 in this embodiment) (refer FIG. 3). In addition, when setting the cross-sectional area of the press member 57 to 1/2 of the cross-sectional area of the cavity 22, it is necessary to size it so that it may not contact the wall surface which defines the cavity 22, for example. . In addition, the shape of the press member 53 can be suitably selected according to the cross-sectional shape of the cavity 22. In addition, it is preferable that the tip of the pressing member 57 is a plane or convex inclined toward the axial front side rather than a plane perpendicular to the axial direction of the pressing member 57.

The fixed frame 51 is provided in two guide rails 58 extending in the direction perpendicular to the pressing direction Y, and the pressing means 5 slides the pressing means 5 along the guide rails 58. (5) Advancing and retreating with respect to this cavity 22 is made free. In this case, the supply device may also be provided on the same guide rail 58 to allow the advance and exit of the cavity 22 to be free. And when it stops with the stopper (not shown) provided in the guide rail 58, the press member 53 is positioned so that a press force may be applied to about half of the area | region of the cavity 22. As shown in FIG.

Here, although not shown in the compression molding machine 1, when the shutter is freely installed on the guide rod 17 and the pressing member 57 is pressed and mixed with the raw material powder P, the shutter is used. By blocking the upper surface of the cavity 22 and mixing the raw material powder by the pressing means 5, a configuration may be adopted in which the alloy powder material P is prevented from jumping out of the cavity 22.

Next, with reference to FIGS. 1-6, manufacture of the Nd-Fe-B type sintered magnet of 1st Embodiment using the compression molding machine 1 is demonstrated. First, each of the upper surfaces of the die 2 and the lower punch 31 are coplanar, and the hydraulic cylinder is operated to operate the hydraulic cylinder from the standby position where the upper punch 32 is located at the upper end (see FIG. 1). The cavity 22 is defined in the through hole 21 by raising it to the position. Then, the powder supply device (not shown) fills the cavity 22 with the raw material powder P previously weighed and added with the lubricant at a predetermined mixing ratio, and the powder supply device is removed. In this case, the packing density of the raw material powder P in the cavity 22 is set in the range of 10-30% with respect to the volume of the cavity 22 in order to leave the freedom of movement of the raw material powder P (FIG. 2). Reference).

Next, the pressing means 5 is positioned so that the pressing member is located in the left half of the cavity 22 above the cavity 22 (see FIGS. 2 and 3). When the piston rod 54a is lowered by operating the cylinder 54, the lifting frame 53 is lowered, and the pressing member 57 is brought into surface contact with the raw material powder P in about half of the area of the cavity 22. (See FIG. 4 (a)). At the same time, a magnetic field is generated by energizing the coils 42a and 42b of the magnetic field generating device 4. In this case, in order to obtain high orientation, it is preferable to press down by the pressing means 5 in a static magnetic field in the range of 0.1 kOe to 10 kOe, preferably 0.5 kOe to 6 kOe. If the strength of the magnetic field is weaker than 0.1 k0e, high orientation and high magnetic properties are not obtained. If the magnetic field is stronger than 10 k0e, mixing becomes difficult.

Then, when the lifting frame 53 is further lowered by the piston rod 54a, the pressing member 57 is pushed into the raw material powder P. As shown in FIG. In this case, it is preferable to set the press pressure of the press member 57 to 1-50 kg / cm <2>. In addition, the pressing means 57 may be vibrated in the pressing direction by a known method. When the pressing member 57 is pushed into the raw material powder P, since the area of the contact surface of the pressing member 57 and the raw material powder P is half of the cross-sectional area of the cavity 22, the pressing member 57 and The raw material powder P is pushed into the space between the inner wall surfaces of the cavity 22 (see Figs. 4 (b) and 4 (c)). Then, after the pressing member 57 is moved just before contacting the lower punch 31 (see FIG. 4 (c)), the lifting frame 53 is raised to raise the pressing member 57 by a predetermined height position. Return to

Next, the movable frame 56 is moved, and it moves so that the press member 57 may be located in the right half of the cavity 22, and it will position (refer FIG. 4 (d)). During this operation, the energization of the magnetic field generating device 4 to the coils 42a and 42b does not stop. And the cylinder 54 is operated, the piston rod 54a is lowered, and the press member 57 is pushed into the raw material powder P (refer FIG. 4 (e) and FIG. 4 (f)). This series of operations is repeated a predetermined number of times (orientation step).

Thus, as in the conventional example, even if the vibration is applied by the upper punch or the lower punch, as shown in Fig. 5 (a), the crystal wavefronts of the mutually adjacent raw material powders P in the magnetic field orientation direction are When it does not match, a gap | interval remains between raw material powders P, and raw material powder P is not aligned in a magnetic field orientation direction, and when compression-molding in this state, an orientation will be disturbed. On the other hand, according to this embodiment, when the magnetic field is applied, the bonding of the bonded particles is once broken, and the raw material powder P is mixed and combined in the magnetic field to be oriented. As a result, the positional relationship between the particles of the raw material powder P in the cavity 22 changes from the state filled in the cavity 22, and the crystal wavefront of the raw material powder P having the same crystal orientation relationship is obtained. When the crystal wavefronts having the same crystal orientation relationship are combined once more opportunities to be combined are formed, by forming a strong binding chain, as shown in FIG. The crystal wavefront is bonded without a gap and is aligned in the magnetic field alignment direction.

Next, when the orientation process is completed, the pressing means 5 is removed. In this case, energization to the coils 42a and 42b does not stop. Then, the die base 16 is lowered, the upper punch 32 is inserted into the through hole 21 from the upper side of the through hole 22, and the upper and lower pairs of punches 31 and 32 are applied in a state where a magnetic field is applied. By this, compression molding of the raw material powder P in the cavity 22 is started. After the lapse of a predetermined time, energization of the coils 42a and 42b is stopped, and compression molding at the maximum pressure is performed in this state (see FIG. 6). Finally, the upper punch 32 is gradually raised and gradually depressurized to end the compression molding, and the molded body M is formed (molding step). As a result, the raw material powder P is bonded to the magnetic field alignment direction without gaps so as to form a rod shape, and compression molding is performed in a state aligned in the magnetic field alignment direction, so that a high-density molded body without the disorder of the orientation is formed. (M) (permanent magnet) can be obtained and magnetic properties are also improved.

In this way, the crystal wavefront is bonded in the magnetic field alignment direction without gaps and compression-molded in a neat state, resulting in a high-density molded article M1 without disorder of orientation, and the strength of the molded article can be strengthened to reduce the occurrence rate of defects. In addition, the molded article M1 (permanent magnet) having high magnetic properties can be obtained. In this case, when the resin binder is mixed with the raw material powder P filled in the cavity 22, a rare earth bond magnet (molded body) having high magnetic properties can be obtained.

The molding pressure in the molding step is set to 0.1 to 2.0 t / cm 2, more preferably 0.2 to 1.0 t / cm 2. At a molding pressure lower than 0.1 t / cm 2, the molded body does not have sufficient strength and, for example, splits when it is taken out from the cavity 22 of the compression molding machine. On the other hand, at a molding pressure of more than 2.0 t / cm 2, a high molding pressure is applied to the raw material powder P in the cavity 22, shaping while breaking the orientation, and there is a fear that gold or cracks may occur in the molded body. . In addition, the strength of the magnetic field in the molding step is set in the range of 5k0e to 30k0e. If the strength of the magnetic field is weaker than 5k0e, it is impossible to obtain high orientation and high magnetic properties. On the other hand, if it is stronger than 50k0e, the magnetic field generating device becomes too large and not realistic.

Then, after demagnetizing by applying a reverse magnetic field of 3 k0e, for example, when the die 2 is lowered to the lower end, the molded body M in the cavity 22 is formed on the upper surface of the die 2. The molded body is removed after the die base 16 is raised to move the upper punch 32 to the ascending end. Finally, the obtained molded body is housed in a sintering furnace (not shown), for example, sintered for a predetermined time (sintering step) at a predetermined temperature (1000 ° C) under an Ar atmosphere, and further, a predetermined temperature (500 ° C) and an Ar atmosphere. In a predetermined time aging treatment, a sintered magnet (Nd-Fe-B sintered magnet) can be obtained.

Next, with reference to FIG. 7, the compression molding machine 10 suitable for manufacturing the rare earth permanent magnet of 2nd Embodiment of this invention, especially the sintered magnet of Nd-Fe-B system is demonstrated. As the compression molding machine 10 carries out the manufacturing method of the said 1st Embodiment, the pressing direction Y (press direction) is a uniaxial pressurized type perpendicular | vertical to the magnetic field orientation direction, and is supported by the leg part 110 It has a base plate 120. The die 20 is disposed above the base plate 120, the die 20 is supported by a plurality of struts 130 penetrating the base plate 120, and the other end of each strut 130 is a base plate ( It is connected to the connecting plate 140 provided below the 120. The connecting plate 140 is connected to a driving means, for example, a cylinder rod 150 of a hydraulic cylinder of a known structure, whereby the lower hydraulic cylinder is operated to raise and lower the connecting plate 140. Is free to move in the vertical direction of FIG. 7 in the pressing direction (Y).

A through hole 210 in an up and down direction is formed in an approximately center portion of the die 20, and a lower punch (25) is installed in the through hole 210 upwardly from an underside thereof to an upper portion in an approximately center portion of an upper surface of the base plate 120. 310 can be inserted, and when the die 20 is lowered by operating the lower hydraulic cylinder, the lower punch 310 is inserted into the through hole 210 so that the cavity (charge chamber; 220) is inserted into the through hole 210. Prepared. The cross-sectional shape of the through hole 210 (cavity 220) is appropriately selected according to the shape of the sintered magnet to be molded, such as a circle or a rectangle. In addition, also in 2nd Embodiment, in order to manufacture a rectangular parallelepiped sintered magnet. The cross-sectional shape is formed in a rectangle.

The die base 160 is disposed above the die 20 so as to face the base plate 120. The upper punch 320 is provided in the lower surface of the die base 160 in the position which can be inserted in the cavity 220. Moreover, the through-hole of the up-down direction is formed in the edge part of the die base 160, and the guide rod 170 whose one end was fixed to the upper surface of the die 20 is inserted through each through-hole. Moreover, the drive rod, for example, the cylinder rod 180 of the hydraulic cylinder (not shown) of a well-known structure is connected to the upper surface of the die base 160, and guides to the guide rod 170 when this hydraulic cylinder is operated. As a result, the die base 160 may freely move up and down, and thus the upper punch 320 may move freely in the up and down direction, and thus may be inserted into the through hole 210 of the die 20. Thereby, at the time of compression molding, the raw material powder P which exists in the cavity 220 is compressed by the upper and lower pair of punches 310 and 320, and a molded object can be obtained.

In addition, the magnetic field generating device is applied to the outer circumference of the die 20 in order to apply a magnetic field when kneading and orienting the raw material powder P in a bag to be described later and when molding the raw material powder P in the cavity 220. (4) is provided. Since the magnetic field generating device 4 is used for the compression molding machine 1, detailed description thereof is omitted here. Moreover, also about raw material powder P, since the same thing as 1st Embodiment can be used, detailed description is abbreviate | omitted here.

In the compression molding machine 10, the kneading means 50 is freely provided in the upper space of the cavity 220 in order to knead and orient the raw material powder P filled in the bag B in a magnetic field. The kneading means 50 has a support frame 510, a plurality of cylinders 520 are mounted on the support frame 510, and nonmagnetic on the piston rod 520a extending downward from each cylinder 520. Pushers (pressing members) 530 which are cylindrical members made of a material are provided respectively. The kneading means 50 also has a frame 550 suspended by a piston rod 540a extending downward from another cylinder 540 mounted to the support frame 510.

The frame 550 has a rectangular columnar shape with an upper surface open, and the inner surface of the side wall is formed such that a plurality of continuous irregularities are repeated. On the other hand, the protrusion part 550a is formed in the center inside the bottom plate of the frame 550. As shown in FIG. In the frame 550, the bag B filled with the said raw material powder P previously weighed is accommodated. The bag B is made of a material free of deformation such as rubber, elastomer, polyethylene, and vinyl. After storing the bag B in the frame 550 and operating the cylinders 520 at the same time or at a time difference, a pressure is applied locally to the bag B by each pusher 530. All. At this time, the bag B is deformed so that its lower center spreads around the protrusion 550a and the side part penetrates into the recess of the side wall. As a result, the raw material powder P in the bag B is kneaded.

Next, with reference to FIGS. 7-11, manufacture of the sintered magnet of the Nd-Fe-B system of 2nd Embodiment using the said compression molding machine 10 is demonstrated. First, in the standby position where the upper surface of the die 20 and the lower punch 310 are coplanar, and the upper punch 320 is located at the upper end (see FIG. 7), the kneading means 50 is applied to the cavity 220. Move upwards of. At that time, the bag B is filled with the raw material P weighed in advance, and the bag B is housed in the frame 550. The packing density of the raw material powder P in the bag B is set in the range of 15 to 55% with respect to the volume of the bag B in order to leave the degree of freedom of movement of the raw material powder P, and the raw material powder ( The volume of the bag B filled with P) is set in the range of 30 to 80% with respect to the volume of the frame 550.

Next, the coils 42a and 42b of the magnetic field generating device 4 are energized to apply a magnetic field. In this case, in order to obtain a high orientation, it is preferable to perform kneading by the kneading apparatus 5 in a magnetic field in the range of 0.1 kOe to 10 kOe, preferably 0.5 kOe to 6 kOe. If the strength of the magnetic field is weaker than 0.1 k0e, high orientation and high magnetic properties are not obtained. If the magnetic field is stronger than 10 k0e, kneading becomes difficult. Then, in a state where a magnetic field is applied, each cylinder 520 is operated at the same time or at a time difference to apply a pressing force locally to the bag B by each pusher 530 (orientation process: FIG. 9). Reference).

Thus, as described above, in the conventional example, even if the vibration is applied by the upper punch or the lower punch, as shown in Fig. 10 (a), the crystal wavefronts of the mutually adjacent raw material powders P in the magnetic field orientation direction are shown. When this does not match, gaps remain between the raw material powders P, and the raw material powders P are not aligned in the magnetic field alignment direction. When compression molding is performed in this state, the orientation is disturbed. On the other hand, according to 2nd Embodiment, since the lower center of the bag B unfolds around the protrusion 550a, and the side part deforms so that it may penetrate into the recessed part of a side wall, the raw material powder in the bag B ( P) is kneaded. In this case, when the magnetic field is applied, the bonding of the bonded particles is once broken and is oriented while the raw material powder P is mixed in the magnetic field. As a result, the positional relationship between the particles of the raw material powder P in the cavity 220 changes from the state filled in the cavity 220, so that the crystal wavefront of the raw material powder P having the same crystal orientation relationship becomes more. Once combined, the crystal wavefronts having the same crystal orientation have more opportunities to be combined, thereby forming a strong binding chain, and as shown in FIG. The wavefront is joined without a gap and is aligned in the magnetic field orientation direction.

Next, the hydraulic cylinder is operated to raise the die 20 to a predetermined position, thereby providing the cavity 220 in the through hole 210. From the bag B, the oriented raw material alloy is taken out and filled. In this case, the filling of the raw material alloy into the cavity 220 can be performed manually. Meanwhile, the lower surface of the frame 550 can be opened and closed freely, and the blade (not shown) is moved forward and backward in the bag B. It is possible to employ a configuration in which a portion of the bag B is torn and automatically dropped to the cavity 220 in a state where it is installed freely and a magnetic field is applied.

Next, when the orientation process is completed, the kneading means 50 is removed. In this case, energization to the coils 42a and 42b does not stop. Then, the die base 160 is lowered, the upper punch 320 is inserted into the through hole 210 from the upper side of the through hole 220, and the upper and lower pairs of punches 310 and 320 are applied in a state where a magnetic field is applied. By this, compression molding of the raw material powder P in the cavity 220 is started. After the lapse of a predetermined time, energization of the coils 42a and 42b is stopped, and compression molding at the maximum pressure is performed in this state (see FIG. 11). Finally, the upper punch 320 is gradually raised and gradually depressurized to end the compression molding, and the molded body M2 is formed (molding step). Also in this case, since the raw material powder P is bonded together without gaps in the magnetic field alignment direction so as to form a rod shape, and compression molding is performed in a state uniform in the magnetic field alignment direction, a high-density molded body without any confusion in orientation ( M2) (permanent magnet) can be obtained, and magnetic properties are also improved.

In this way, the crystal wavefront is bonded without gaps in the magnetic field alignment direction and compression-molded in a neat state to form a high-density molded article M2 without disordered alignment, and the strength of the molded article is strengthened, which can reduce the incidence of defects. In addition, the molded article M2 having high magnetic properties can be obtained. In this case, when the resin binder is mixed with the raw material powder P filled in the cavity 220, a rare earth bond magnet (molded body) having high magnetic properties can be obtained.

The molding pressure in the molding step is set to 0.1 to 2.0 t / cm 2, more preferably 0.2 to 1.0 t / cm 2. At a molding pressure lower than 0.1 t / cm 2, the molded body does not have sufficient strength and, for example, splits when it is taken out from the cavity 220 of the compression molding machine. On the other hand, at a molding pressure of more than 2.0 t / cm 2, a high molding pressure is applied to the raw material powder P in the cavity 220, shaping while breaking the orientation, and there is a risk of cracking or cracking in the molded body. . In addition, the strength of the magnetic field in the molding step is set in the range of 5 kOe to 30 kOe. If the strength of the magnetic field is weaker than 5k0e, it is impossible to obtain high orientation and high magnetic properties. On the other hand, if it is stronger than 30k0e, the magnetic field generating device becomes too large and not realistic.

Then, for example, after applying a reverse field of 3 k0e to perform demagnetization, when the die 20 is lowered to the lower end, the molded body M in the cavity 220 is pulled out on the upper surface of the die 20, The molded body is taken out after raising the die base 160 to move the upper punch 320 to the rising end. Finally, the obtained molded body is housed in a sintering furnace (not shown), for example, sintered for a predetermined time (sintering step) at a predetermined temperature (1000 ° C) under an Ar atmosphere, and further, a predetermined temperature (500 ° C) and an Ar atmosphere. In a predetermined time aging treatment, a sintered magnet (Nd-Fe-B sintered magnet) can be obtained.

In addition, although the said 1st and 2nd embodiment demonstrated the thing of the uniaxial pressurization type in which the shaping | molding direction was perpendicular | vertical to the direction of a magnetic field, it is not limited to this, The compression which the direction of a shaping | molding direction and a magnetic field becomes parallel is You can also use a molding machine. Here, in 1st Embodiment, although shaping | molding powder using the uniaxial-pressure type compression molding machine 1 was demonstrated, the hydrostatic pressure molding machine (not shown) of well-known structure using a rubber mold can be used.

Further, in the first and second embodiments described above, a static magnetic field in which the strength of the magnetic field per unit time does not change is used as the orientation magnetic field during pressing or kneading and molding, but the present invention is not limited thereto. A pulsating pulse magnetic field in which the intensity of the magnetic field changes at regular intervals may be used. In this case, the reverse magnetic field may be applied. Thereby, since vibration can be applied with respect to the raw material powder P at the time of shaping | molding, orientation can be improved further. The period of the pulse is preferably 1 ms to 2 s, and the non-output time is preferably set to 500 ms or less. If it exceeds this range, a strong binding chain is broken and high orientation cannot be obtained. Moreover, when applying a pulsating pulse magnetic field, it is preferable to set the peak value in the range of 5-50k0e. If the strength of the magnetic field is weaker than 5k0e, it is impossible to obtain high orientation and high magnetic properties. On the other hand, if it is stronger than 50 k0e, the magnetic field generating device becomes too large, and the durability of the device becomes low, which is not realistic.

In addition, although the manufacture of a sintered magnet was demonstrated as an example in the said 1st and 2nd embodiment, the orientation which polarized powder in a magnetic field or an electric field was orientated, an orientation body was produced, or this orientation in a magnetic or electric field was compression-molded, In addition to or instead of compression forming, if the sintered magnetic or electric field oriented or compression molded is sintered, the method for producing a permanent magnet of the present invention can be applied or applied. For example, (Tb, Dy) Fe ₂ based super magnetostrictive material, SrO 6 Fe ₂ O ₃ based material, (Sr, La) O 6 (Fe, Co) ₂ O ₃ based ferrite sintered magnet, SmFe ₁₇ based nitride It can be applied to the production of bonded magnets, Nd-Fe-B-based HDDR bonded magnets, etc., and also to be applied to the production of silicon nitride (Si ₃ N ₄ ) sintered bodies formed by sintering a predetermined powder in a magnetic field. Can be.

(Example 1)

In Example 1, an Nd-Fe-B-based raw material powder was produced as follows, an alignment step and a molding step were performed using the following molding apparatus to produce a predetermined molded article, and then 1050 under Ar atmosphere. The sintering process of sintering this molded object was performed for 3 hours at the temperature of ° C, and the sintered magnet of Nd-Fe-B system was obtained.

<Raw powder> As a sintered magnet of Nd-Fe-B system, the composition is 22Nd-7Pr-0.95B-1Co-0.2Al-0.05Cu-0.1Zr-0.05 Ga-bal. Using Fe, an alloy was produced by the strip casting method, and the alloy was subjected to hydrogen pulverization (hydrogen pulverization step) in 0.2 atm of hydrogen gas for 3 hours, followed by vacuum dehydrogenation at 500 ° C for 3 hours.

Subsequently, the fine mill was pulverized by a jet mill pulverization process, and the half width of the powder particle size distribution was 10 µm (raw material powder A), 4 µm (raw material powder B), and 2 µm (raw material powder C) with an average particle diameter of 3 µm. The raw material powder P of was produced, respectively.

<Orientation process> The uniaxial press molding machine 1 shown in FIG. 1 was used as an orientation process. Here, the compression molding machine 1 is comprised so that a 20 k0e static magnetic field may be applied to the cavity 22 which has a 50 * 50mm square opening part. First, the raw material powders A, B, and C were filled into the cavities 22. Prior to filling, 0.3% of a fixed lubricant (zinc stearate) was added to a specific alloy raw material, and the filling depth of 75 mm was filled with a filling density of 25%. And while applying the magnetic field of 4k0e, the pressing force was set to 10 kg / cm <2> and the raw material powders A, B, and C were pressed down by the pressing means 5, and it orientated. The conditions, such as the shape of the press means 5 and the number of times of pressing at this time, are shown to FIG. 12 (a).

<Molding process> As the forming process, using the uniaxial press-type compression molding machine 1 shown in FIG. 1, compression molding is performed by using a pair of upper and lower punches 31 and 32 while applying a magnetic field of 20 k0e to the orientation. Was carried out (molding step). The molding pressure in this case was set to 0.5 t / cm 2. After the compression molding, a reverse magnetic field of 2 k0e was applied and demagnetization was carried out, and then the molded body was taken out of the cavity 22.

<Sintering process> The said molded object was sintered using the sintering furnace which has a well-known structure. In this case, sintering temperature was performed at 1050 degreeC for 3 hours. Prior to sintering, hydrogen was made to flow in 100 Pa vacuum between 100 degreeC and 500 degreeC, and the binder removal process was performed. Immediately after the debinding treatment, the flow of hydrogen was stopped and dehydrogenation was carried out to a vacuum degree of 10 ^-5 Pa. After sintering, the sintered magnet was heat treated at 500 ° C. for 2 hours, and then cooled to room temperature.

12 (b) is a table showing the magnetic properties and the degree of orientation when a sintered magnet is obtained by changing the type of raw material powder, the pressing method by the pressing means, and the like. The magnetic property is an average value of the results evaluated by the BH tracer, and the degree of orientation is a value obtained by dividing the value of the residual magnetic flux density by the saturated magnetic flux density at 10T.

According to this, it turns out that the orientation degree and the coercive force are improving so that the half value width of the particle size of raw material powder becomes narrow (sharp). Moreover, it turns out that orientation degree improves so that the frequency | count which a pressing means presses increases. In addition, it is understood that the pressing means is a nonmagnetic material, and the orientation degree is improved when the lubricant is added to the raw material powder. On the other hand, it can be seen that the tip of the pressing means is sharp, and the degree of orientation improves when the longitudinal vibration is applied.

(Example 2)

In Example 2, an Nd-Fe-B-based raw material powder was produced as follows, an orientation process and a molding process were performed using the following molding apparatus to produce a predetermined molded article, and then 1050 under Ar atmosphere. The sintering process of sintering this molded object was performed for 3 hours at the temperature of ° C, and the sintered magnet of Nd-Fe-B system was obtained.

<Raw powder> A sintered magnet of Nd-Fe-B system, whose composition is 23Nd-7Pr-0.98B-1Co-0.2Al-0.1V-0.05Sn-bal. An alloy was produced by strip casting using Fe, and the alloy was subjected to hydrogen pulverization (hydrogen crushing step) for 3 hours in hydrogen gas at 0.2 atm, followed by vacuum dehydrogenation treatment at 500 ° C for 3 hours.

Then, it grind | pulverizes by a jet mill grinding | pulverization process, the half value width of powder particle size distribution is 10 micrometers (raw material powder A), 6 micrometers (raw material powder B), 2 micrometers (raw material powder C), and an average particle diameter is 5 micrometers. The raw material powder P of was produced, respectively. At that time, 0.3% of fixed lubricant (zinc stearate) and 0.5% of methyl caproate were appropriately added.

<Orientation process> As the orientation process, the uniaxial press-type compression molding machine 1 shown in FIG. 7 was used. In this case, it was accommodated in the urethane rubber bag B of thickness 0.02mm and volume 500cc by the weight of 800g. After storing the bag B in the frame 55, each pusher is operated for 5 seconds alternately in a 0.5 second cycle by using three pushers 530 capable of applying a pressure of 5 kg. The coil 42a, 42b of (4) was energized, the 1 kOe static magnetic field was applied, and the alloy raw material in the bag was kneaded in the magnetic field and orientated (orientation process).

<Molding process> As a molding process, it compresses by a pair of upper and lower punches 310 and 320, applying a 25 k0e static magnetic field to the said orientation using the uniaxial press-type compression molding machine 10 shown in FIG. Molding was carried out (molding step). In this case, the cavity 220 had an opening of a 75 × 75 mm square, and the molding pressure was set at 0.4 t / cm 2. Then, after compression molding, an inverse magnetic field of 3 k0e was applied, and after demagnetizing, the molded body was taken out of the cavity 220.

<Sintering process> The said molded object was sintered using the sintering furnace which has a well-known structure. In this case, sintering temperature was performed at 1050 degreeC for 3 hours. Prior to sintering, hydrogen was made to flow in 1 Pa vacuum between 100 degreeC and 500 degreeC, and the binder removal process was performed. Immediately after the debinding treatment, the flow of hydrogen was stopped and dehydrogenation was carried out to a vacuum degree of 10 ^-3 Pa. After sintering, the sintered magnet was heat treated at 500 ° C. for 2 hours, and then cooled to room temperature.

Fig. 13 is a table showing magnetic properties and orientation when a kind of raw material powder is changed to obtain a sintered magnet, and the table is filled with 800 g of raw material powder without kneading, under the same conditions as in the above-described embodiment. The magnetic properties and orientation degree when a sintered magnet was obtained are shown together (comparative example). In addition, a magnetic property is an average value of the result evaluated by BH tracer, and orientation degree is a value obtained by dividing the value of residual magnetic flux density by the saturation magnetic flux density in 10T.

According to this, it turns out that the orientation degree and the coercive force are improving so that the half value width of the particle size of raw material powder becomes narrow (sharp). Moreover, when kneading a raw material powder at the time of an orientation process, it turns out that an orientation degree improves and especially a maximum energy level becomes high. In addition, it can be seen that the degree of orientation is improved by adding the lubricant.

1, 10 compression molding machines
2, 20 die
21, 210 Through Hole
12, 220 joint
11, 32 punch
4 field generator
5 pressing means
57 pressing member
50 kneading means
530 pusher
P raw powder

Claims (9)

The raw material powder is filled into the filling chamber, and the raw material powder is oriented in a magnetic field while pressing the pressing means having an area smaller than the cross sectional area of the filling chamber, and the molded product is compression molded into a predetermined shape in the magnetic field. Method for producing a permanent magnet, characterized in that it comprises a molding step. The method of manufacturing a permanent magnet according to claim 1, wherein the positions of the pressing means are sequentially changed so that the pressing means is pressed over the entire cross section of the filling chamber. The method of manufacturing a permanent magnet according to claim 1 or 2, wherein the pressing means vibrates in the pressing direction when the pressing means is pressed. The method of manufacturing a permanent magnet according to any one of claims 1 to 3, wherein the raw material powder is filled in a filling chamber after mixing with a lubricant at a predetermined mixing ratio. The method of manufacturing a permanent magnet according to any one of claims 1 to 4, wherein the pressing means is a nonmagnetic material. Filling the raw material powder into a bag free of deformation,
Applying a local pressing force to the bag to orient the material powder in the bag while kneading the magnetic field;
And a step of compressing and molding the oriented raw material powder into a predetermined shape in a magnetic field. The method of manufacturing a permanent magnet according to claim 6, wherein a lubricant is added to the raw material powder at a predetermined mixing ratio and mixed, and then filled into a bag. The method of manufacturing a permanent magnet according to any one of claims 1 to 7, including a sintering step of sintering the oriented or compression molded product in addition to or instead of the molding step. The method of manufacturing a permanent magnet according to any one of claims 1 to 8, wherein the raw material powder is for a rare earth magnet produced by a quenching method.

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